The reductive pyrolysis of a carboxylic acid or ester, i.e. of a substrate wherein the carboxylic functional group is not part of a ring, into the corresponding aldehyde or ketone is a quite known type of reaction. For example, one may cite the processes described in U.S. Pat. No. 2,053,845 or more recently in U.S. Pat. No. 4,950,799.
In contrast, to the best of our knowledge, the reductive pyrolysis of a substrate wherein the carboxylic functional group is part of a ring has been reported only once, in EP 539274, wherein a cyclic anhydride is reduced into the corresponding di-aldehyde.
In fact the general formulae of the substrates described in the prior art, and in particular in EP 539274, exclude the use of lactones as reactant. The prior art does not teach, nor suggest, a process for the reductive pyrolysis of a lactone, and even less the reduction, into the corresponding unsaturated aldehyde or ketone, i.e. a reaction wherein in a single step there is reduced a carboxylic function and a carbon-carbon double bond is formed in a specific position.